1. Field of the Invention
The present invention relates to a heat dissipating fan and, more particularly, to a heat dissipating fan including a motor having an inner rotor.
2. Description of Related Art
FIG. 1 shows a conventional heat dissipating fan including an outer-rotor-type motor. Specifically, the heat dissipating fan includes a frame 51, a stator 52, a circuit board 53, and a rotor 54. An axle tube 511 is formed in the frame 51 and receives at least one bearing 512. The stator 52 and the circuit board 53 are mounted around the axle tube 511, with the stator 52 electrically connected to the circuit board 53. The rotor 54 includes a shaft 541 and an impeller 542 mounted to an end of the shaft 541. The shaft 541 is extended into the axle tube 511 and rotatably held by the bearings 512. The impeller 542 includes a permanent magnet 543 facing the stator 52. The circuit board 53 controls the stator 52 and the permanent magnet 543 to proceed with energizing for creating an alternating magnetic field to drive the impeller 542 to rotate for heat dissipation purposes.
Motors of an outer rotor type are generally less stable in rotation than those of an inner rotor type. Currently existing heat dissipating fans often utilize outer-rotor-type motors as a driving device for dissipating heat in various electronic products. The current trend of research and development of electronic products includes high speed, function integrity, and miniaturization, which also have increased need for heat dissipation. Unfortunately, the conventional heat dissipating fans having outer-rotor-type motors can not fulfill the heat dissipation need of these electronic products.
To meet higher heat dissipating need, heat dissipating fans having inner-rotor-type rotors are utilized, and an example of which is disclosed in Taiwan Patent Publication No. 200744290 entitled “FAN AND ITS INNER-ROTOR-TYPE MOTOR.” As illustrated in FIG. 2, the conventional inner-rotor-type motor includes a housing 61, a stator 62, a rotor 63, and a driving device 64. The housing 61 is comprised of a first housing 611 and a second housing 612. The stator 62 includes a magnetically conductive member 621 to which the driving device 64 is electrically connected. The rotor 63 includes a shaft 631 extending through the housing 61 and a magnetic element 632 mounted around the shaft 631 and facing the magnetically conductive member 621. The driving device 64 controls the current direction of the magnetically conductive member 621 to cooperate with the magnetic element 632 for generating an alternating magnetic field to drive the rotor 63 to rotate. An impeller 65 can be coupled to the shaft 631 to form a fan. However, the housing 61 must be mounted inside a fan housing (not shown) when it is desired to dissipate heat in various electronic products with such a fan. Air current generated by rotation of the impeller 65 can be guided to a heat-generating portion in an electronic product for heat dissipating purposes. However, mounting of the conventional heat dissipating fan having an inner-rotor-type motor in the fan housing is troublesome. Furthermore, the driving device 64 (i.e., the circuit board) is mounted at a location near the stator 62 that generates a large amount of heat during operation. As a result, damage to electronic elements is liable to occur, for heat dissipation of the driving device 64 is not easy.